How to Fix a Toilet Water Supply Line Leak: 5 Easy Steps

Last Updated On July 14, 2024

Updated on August 30, 2022



Reviewed by

How to Fix a Toilet Water Supply Line Leak 5 Easy Steps

Do you have a leak coming from your toilet water supply line? You need to fix the leak immediately before it becomes a serious problem. Not only can it lead to higher water bills, but expensive water damage to your bathroom as well. 

In this PlumbingNav guide, we will cover:

  • Understanding your toilet
  • Is your toilet leaking from the tank water supply connector hose?
  • How to fix a toilet water supply line leak
  • How to fix a leaking toilet hose connector
  • Supplies you’ll need to fix a toilet water supply line leak

What's In This Guide?

      Understanding Your Toilet

      Before you fix a toilet water supply leak, it’s a good idea to understand how a standard toilet works and where hoses come in. Spoiler, they are crucial and get used frequently. 

      As the name suggests, the water supply line supplies water to your toilet from your home’s main water supply ⅜” in diameter.

      The fill valve opens to allow water into the toilet tank when you flush the toilet and empty the tank. A ball connected to the fill valve closes the fill valve as the toilet tank reaches a certain water level. All of this water flows through the supply line and connector when refilling the tank each time.

      If for some reason the fill valve doesn’t close all the way, an overflow tube removes excess water from the toilet tank to prevent water damage. 

      With a full tank and the fill valve closed, the toilet water waits patiently until someone uses it. 

      When someone uses the toilet, they flush the toilet. Flushing the toilet opens the flush valve, sending water into your toilet bowl. If you didn’t have supply line hoses, the toilet tank wouldn’t be able to fill back up

      See the video below to learn more about how your toilet works, if you’re curious and want to impress your friends:

      What You Need to Know About How to Fix a Toilet Water Supply Line Leak

      If you experience a supply line toilet leak, it can use a lot of water in the bathroom and cause significant water damage. Water damage from a faulty toilet costs anywhere from $2000 – $10,000 per incident. 

      If you knew about the small leak and didn’t fix it, it could impact this plumbing issue being covered by your homeowner’s insurance policy.

      You should inspect your toilet supply line roughly every 6 months, especially if it’s an older toilet. Don’t forget to check that the shutoff valve works in the case of an emergency as well. It’s important to know how to turn the water off to your toilet ahead of time.

      You will find the supply line connector hose behind the toilet near the bottom. In most cases, you can find the shut-off valve at the wall connection. The supply line may be inside your wall if you have a tankless toilet.

      Supply lines usually consist of stainless steel coating and PVC or rubber tubing inside.

      Is Your Toilet Leaking From the Tank Water Supply Connector Hose?

      You can confirm your toilet is leaking from the tank water supply connector if you see water dripping from the water supply pipe. Now, if it’s hot and humid this might be sweat. However, condensation from “sweat” often isn’t a steady drip.

      The leaky supply line will be most noticeable when you flush the toilet since that’s when water will enter your toilet tank. 

      Sometimes it can be difficult to distinguish between a leak coming from the wax seal around your toilet base and the supply line. 

      Alternatively, you may experience a problem with the water supply valve inside of the toilet tank as opposed to the supply line itself. Check that the valve looks clean and in working order to eliminate the valve as the cause of the problem.

      Common Causes Of The Toilet Connector Hose Leaking

      Your toilet connector hose might leak if it gets old and starts to deteriorate due to corrosion or old age. While plastic hoses won’t experience corrosion the same way as metal ones, they will still wear down over time. 

      Your toiler water supply hose may also leak if it doesn’t have a secure connection. You may need to tighten the connection or replace the connectors. Also, the O-ring inside might simply be faulty (or missing.)

      Sometimes, the hose will leak if it experiences trauma that creates a hole in it. Trauma, you say? Yes, sometimes they get kicked or pulled during sweeping, mopping, or cleaning. 

      did you know how to fix water line supply lines

      How To Fix a Leaking Toilet Hose Connector (5 Step Guide)

      Toilet hose repair doesn’t need to go to the professionals. Use these five simple steps to fix a leaky toilet supply line leak yourself!

      Step One: Identify the Location of the Toilet Water Supply Line Leak

      The leak may occur in numerous different locations throughout the toilet water supply line. 

      Use a rag to run it over the supply line to identify the leak’s location. You will know once the rag gets wet. You can also use a paper towel, as this will spot up easily and obviously. 

      If the rag gets wet at the connections, pay attention to if the wetness occurs at the top or bottom of the supply line connection. If the wetness occurs on the line itself, it may have a small hole in it.

      Step Two: Replace Supply Line Washers

      Washers help prevent leaks inside the connectors. Sometimes, washers lose effectiveness. 

      You can remove the fitting to gain access to the old washer. Remove it and replace it with a washer the same size.

      Step Four: Apply Sealant to Threads

      Use sealant, such as plumber’s tape, around the connections to ensure a tight seal. Apply the plumber’s tape to the threads in the connections and then reattach the connections.

      Don’t use a sealant that will dry, such as adhesives or clear caulk. That will make for a very bad day in the future when you need to remove the hoses.

      Step Three: Tighten/Replace Connections

      After you replace the washers and apply sealant, tighten the connections using your hands or a plumber’s wrench. Don’t tighten them so much that you strip them. If the leak still occurs at the connections, you may need new fittings.

      Step Five: Replace Toilet Water Supply Line Hose

      If all else fails, you will need to replace the toilet supply hose. Luckily, the task is easy enough for any novice DIY plumber. They are inexpensive, too. All you need to do is remove the old hose and attach the new universal supply hose.  

      See the video below to learn more about how to replace your toilet supply hose:

      Supplies You’ll Need to Fix a Toilet Water Supply Line Leak


      Purchase washers specifically designed for your supply hose connectors. You may want to purchase a package of faucet and toilet washers in multiple sizes.

      Plumber’s Tape

      Plumber’s tape creates a tight seal in plumbing connections that use threads. In most cases, plumbers tape comes ½” wide.

      You will apply the plumber’s tape into the threads to prevent water from seeping through them. You can use plumbing tape to fix a water supply line leak at your toilet but also numerous other plumbing applications.

      Plumber’s Wrench

      Every DIY plumber needs an adjustable wrench that will grip onto bolts and pipes of different sizes. 

      FAQs For Toilet Water Connection Leaks

      Why is my toilet supply line leaking?

      Age causes toilet supply leaks more than anything else. The hose and connections may deteriorate over time.

      Leaks may also occur in new supply lines if connections get loose or the hose experiences trauma.

      How do you seal a toilet supply line?

      Use plumbers tape to fill in the threads before establishing the connection.

      How do I fix a leaking water supply?

      Fix a leaking water supply line by replacing washers and tightening/replacing the connectors. If that doesn’t work, replace the water line, especially if it’s old.

      Related Content: Need to know how to remove a toilet? See this post for 5 easy steps…

      Meet Your Plumbing Navigator

      Plumbing Navigator: plumbing advice

      About Plumbing Navigator

      We’re passionate about all things plumbing, and love sharing tips, “how-to”, and reviewing the latest products to help make your project a success!

      Learn More Plumbing Tips

      Want to tackle more plumbing projects? Check out these helpful guides!

      best water heater stand
      tankless water heater flush kit
      best mesh drain strainer
      Best Shower Drain Cover

      Got Plumbing Questions? Search For In-Depth Answers Below!

      About Plumbing Navigator

      We write about "all things plumbing," helping you navigate common questions, repairs, and the best plumbing products on the market.

      About Plumbing Navigator

      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

      Recently Published Guides